As investigators worked to pinpoint the cause of a series of dramatic natural gas explosions in three towns north of Boston, Massachusetts, Gov. Charlie Baker toured the neighborhood where an 18-year-old was killed by a falling chimney. (Sept. 14)
AP

Flames consume the roof of a home in Lawrence, Massachusetts, as shown in a video provided by WCVB in Boston. The pressure in natural gas pipelines before the explosions last week was 12 times higher than it should have been.(Photo: WCVB via AP)

The pressure in the natural gas pipelines under three Massachusetts communities spiked to 12 times their normal level last week, just before the explosions and fires that destroyed dozens of homes and killed an 18-year-old man, according to Sens. Ed Markey and Elizabeth Warren.

The Massachusetts Democrats were briefed on the explosions in and around Lawrence by the National Transportation Safety Board, which is investigating.

Markey and Warren are demanding answers from Columbia Gas and its parent company about the utility's response to the pressure readings.

But it's unclear what Columbia Gas did with that information. Markey and Warren want to know whether the company reported it to state and local authorities. They also want to know why the utility waited until 9 p.m. – more than four hours after the first blasts – to publicly acknowledge the catastrophe.

The cascading series of fires and explosions in the Northeastern Massachusetts towns of Lawrence, Andover and North Andover destroyed as many as 80 homes and buildings, injured dozens and killed 18-year-old Leonel Rondon. Rondon was sitting in a car when the chimney of an exploding home fell on its roof.

More than 8,600 gas customers were evacuated from their homes for days while utility crews worked to restore service.

Massachusetts Gov. Charlie Baker, angered by what he saw as a slow response from Columbia Gas, declared a state of emergency last Friday and put another utility company in charge of the effort.

A spokesman for Columbia Gas parent company NiSource called the explosions "an unprecedented situation."

"We were working as quickly as we could to take care of the customers and stabilize the situation," spokesman Ken Stammen said.

He said the company was cooperating with state and local investigators and was crafting a response to the senators' letter.

"We're as anxious as anybody else to learn what went wrong last Thursday."

The senators are seeking hearings in the Senate Commerce Committee. The NTSB hopes to have a preliminary report on the cause within a few weeks, spokesman Keith Holloway said.

"It is imperative that the people of the commonwealth ... understand what caused this disaster and how you responded to it, in order to ensure that we never again face a similar tragedy," the senators wrote in their letter.